1. Field of the Invention
The present invention relates to an air conditioning system using ground heat, and more particularly, to an air conditioning system performing heat exchange using ground heat, and including an auxiliary heat source that can be selectively used to assist heat exchange.
2. Description of the Related Art
Generally, an air conditioning system called an air conditioner a cooling/heating system for cooling an indoor space through repetition of sucking warm indoor air, exchanging heat with coolant of low temperature, and discharging the indoor space, or for heating the indoor space through a reverse operation. The air conditioning system provides a series of cycles of a compressor-condenser-expansion valve-evaporator.
Also, recently, the air conditioning system also provides an air conditioning function of sucking and filtering polluted air of the indoor space, purifying the polluted air into clean air, and supplying the clean air back to the indoor space, and a variety of additional functions such as a dehumidifying function of changing humid air into dry air and supplying the dry air back to the indoor space.
Meanwhile, as is generally known in the art, an air conditioner is roughly classified into a separation type air conditioner where an outdoor unit and an indoor unit are separately installed, and an integral type air conditioner where the outdoor unit and the indoor unit are integrally installed.
Also, recently, a multi-type air conditioner is brought to the market. The multi-type air conditioner can be effectively used in the case where two or more air conditioners are installed in home, or air conditioners are installed at respective offices of a building having a plurality of offices. The multi-type air conditioner can achieve an effect as if a plurality of separation type air conditioners were installed by connecting a plurality of indoor units to a single outdoor unit.
However, a related art air conditioner maintains an indoor space at an appropriate state through a heat exchange operation between coolant of the inside of the air conditioner and outside air. Therefore, temperature of outside air is too low during a heating cycle, and too high during a cooling cycle in a heat exchange system using the air.
Therefore, great energy is consumed in absorbing and exhausting heat from coolant. When temperature of outside air is not constant, it is difficult to stably operate a cooling cycle and a heating cycle due to abnormality of a heat source required for the heating/cooling cycles.
Meanwhile, to solve problems of a heat exchange system using outside air, there recently emerges a basic air conditioning system performing outside heat exchange using ground heat as a heat source. Therefore, since the air conditioning system using the ground heat exchanges heat using ground heat as a heat source without an influence caused by temperature of outside air, it provides higher thermal efficiency (coefficient-of-performance (COP) and energy efficiency ratio (EER)) than that of an air conditioning system using air.
However, an air conditioning system using ground heat has lots of problems. That is, despite advantages such as thermal efficiency improvement, the air conditioning system using ground heat still has a problem that stability and reliability of cooling/heating cycles decreases when coolant that has flowed through an outdoor heat exchanger after it exchanges heat in an indoor space does not sufficiently exhaust/absorb heat to/from the ground during cooling/heating cycles.